Purpose: The posterior transarticuar screw fixation C1-2 (Magerl) is a demanding procedure to treat atlanto-axial instabilities. In spite of a high primary instability it holds risks to injure the A. vertebralis as well as neurological structures. Furthermore the posterior approach of the upper part of the cervical spine requires a huge and traumatic preparation of the soft tissue. However the anterior transarticular C1-2 fusion is less traumativc and offers approximately the same strengh of the stabilisation.
Methods: Since the beginning of 2007 17 multimorbid patients with atlanto-axial instabilities of different entities were treated via the anterior transarticular fusion, were regular examined radioogicaly (x-ray/CT) and the procedure critically judged.
Results: C1-2 fusions were performed in 17 patients (13f, 4m, average 81,6 years (68.95)). The main symptoms was pain radiating in the upper cervical spine and the occiput, 2 Patients complaining radiating pain with paraesthesia in both upper extremities, whereas the neurology was predoinant inconspicious. The average operation-time took 64,5 min. On the left side the screws of Ø 39,5mm (32–44mm), on the right side of 36mm (32–44mm) were inserted in addiction to the point of access and the angle of insertion (mediolateral angle Ø 32,0°, ventrodorsal Ø17,6°). There were no intraoperative complications concerning the ceratin procedure, postoperative one revision had to be done because of p.o. bleeding, another because of screw dislocation with clinical relevance 21 days after the first operation. The postoperative x-ray and CT control of the upper cervical spine showed 21/34 screws in 17 patients in correct position (61,7%), 7 (20,6%) screws were too long, 6 (17,7%) screws were placed too anterior and too medial compared to the oppinion of literature. position in the literature. 3 additional positionated dens-screws were in correct position. After a clear learning curve both screws of the 6th patient were positoinated correct. In this connection it could be shown, that two aspects are important for success: A correct entry point as well as the right insertion of the angle of the screws in the coronar and sagittal view. A low intraoperative blood loss, a non traumatic access as well as an immediate postoperative pain decrease have to be valued positively for this procedure.
Conclusions: The gentle procedure of the anterior transarticular C1-2 fusion requires-despite of the huge experience in anterior surgery of dens fractures – a learning curve, because of the more proximate insertion point, the flat insertion angle and the closeness of the A. vertebralis. If these aspects are going to be noticed, failed screw positioning and excessive length as well as injuries of the A. vertebralis can be avoided.
